Divide dough into 30 equal portions. Working with 1 portion at a time (cover remaining portions to keep dough from drying out), roll into a 4-inch circle on a lightly floured surface. Spoon 2 heaping tablespoons cabbage mixture onto half of circle. Fold dough over filling; press edges together with a fork to seal. Place turnovers on a baking sheet coated with cooking spray, and brush with egg white. Repeat procedure with remaining dough, cabbage mixture, and egg white.